[Merged]Freeview aerial installation - Page 3

Hornet · 20-06-2007, 14:34

Sandy Heath and Oxford one is 23 miles and other 24 miles.

I have gained 10 digital channels not listed for my postcode on freeview that I didn't have via loft install. Plus my digital box receives the ALL at 100% mark. Used to receive Sky news at this level, but BBC1,2 ITV, 4 channels were 50% to 75%.

Get analogue fine on everything except BBC2, yet used to get BBC2 analogue fine in loft.

Aerial is now pointing slightly more left than straingt in loft.

Is it just one of those things or do I need to get them back again should I be getting analogue BBC2 fine?

Cheers

altis · 20-06-2007, 15:33

I can't see any reason why you shouldn't receive BBC2 well on analogue.

It looks like you may be pointing at Sandy Heath (near Bedford). Of the two, this is the more powerful transmitter 1 Megawatt for analogue vs 500 MW for Oxford. The digital channels are also stronger - all 20 kW vs 10, 8 and 6 kW for Oxford.

The range of frequencies used will put great demands on your aerial - whichever transmitter is used. For Sandy Heath they range from channel 21 to 67 and for Oxford it's 27 to 68. The maximum range available is 21 to 68 so you'll definately need a wideband antenna (colour coded black).

BBC2 on analogue is on channel 63 from Oxford and 27 from Sandy Heath. These are not off the end of the range as I was expecting. It seems that, instead, that your aerial is so good that you are picking up some interference from yet another transmitter. Do you see wavy lines on the screen or just snow. I suggest that you try fine tuning the TV to see if you can get a better signal.

Hornet · 20-06-2007, 15:35

Wavy lines on one and snow on the other as two 2's have tuned in! So is it worth getting them back or just leave it. I have the top aerial they do with mast amp

altis · 20-06-2007, 15:57

Great! That gives us a lot of information. The wavey BBC2 will be the 'real' one that you're looking for. The snowy one will be coming from a distant transmitter. Another channel from the distant transmitter will be interfering with your local BBC2.

Which channel is the wavey BBC2 on?
Which channel is the snowy BBC2 on?

And I guess a rough idea of your location would be useful - eg. nearest town or village.

Hornet · 20-06-2007, 17:47

Grainy BBC2 is 44

Wavy BBC2 is 27

Perfect BBC1 is on 31.

Leighton Buzzard, Beds, LU7

carpy · 20-06-2007, 19:42

Looks like you're lined up on Sandy.

The wavy pattern on BBC2 analogue is because the idiot from Action Aerials doesn't have a clue what he's doing & probably doesn't even have a decent spectrum analyser to see what the problem is on CH27.

My guess would be the amplifier is being overloaded with the strong analogue signals. Try fitting a 6db attenuator on the end of the cable before it goes into the amplifier. This will almost certainly cure the problem completely.

A decent installer would test this & know exactly what the problem is in about 1 minute. Where do they get these idiots from?

Hornet · 20-06-2007, 20:04

Will this affect the other cahnnels though? Does it mean he should come back and reposition the aerial really? Or would that not help. He said he only worried about lining it up to the best digital signal.

Are you saying I need to fit something to my 4 way amp in the loft or the part that is in the plug socket next to the aerial point, which it is then connected too?

carpy · 20-06-2007, 20:25

Fit a 6db attenuator onto the aerial cable, in the loft, just before it goes into the 4 way amplifier. You can get one of these from Maplins, or buy from the internet. You'll need to go into the loft and disconnect the aerial cable (from outside aerial) from the 4 way amplifier to see what kind of connector it has. You'll need to buy an attenuator with this same connection type. It's either going to be F type (screws on) or the usual Belling Lee (normal coax plug pushes in).

If it's not the amplifier being overloaded then it's going to be RF inteference and I'd be a bit worried about what this is doing to the BER (Bit Error Rate) of the digital muxes.

If you're worried about the analogue signals then you might want to get them back to sort it out, but if you've got Freeview everywhere then it's not as much of an issue assuming the Freeview signals have been measured correctly and are robust.

pedantic · 20-06-2007, 20:34

Try something like these, the adjustable ones will probably be better.

Hornet · 20-06-2007, 22:16

I am getting more stressed now over action aerials.

I've watched CH4 for about an hour through digital and BBC1 (digi box again) both glitched/pixelated about three times for a second over the hour, so about 6 freezes in two hours.

But BBC2 analogue has now corrected itself, picture 100% fine, haven't touched anything????

My digi boxes one in bedroom one in lounge used to read 50% for CH4, BBC1 and glitch every 10 mins. Sky Sports news, three and news were always 100% and still are. NOW ALL CHANNELS are 100% signal on both boxes yet I'm still getting odd freezes/glitches.

I have quiried why my aerial is roof level and not a foot higher like other 100 or so on estate, I was told no house opposite me like all of the others, I look up a road. Therefore no need to be a foot above my own roof. Also reading son techs machine show aerial sited fine.

Is my signal too strong and that is why I am still getting digital glitches or should my aerial be raised a foot?

When I complained about BBC2 they said call us Friday when you've had a chance to see if everything else OK, which is fair enough.

Engineer today said I am losing a lot of signal strength in my internal cables as in the loft the signal on his reader is very strong, yet at TV points it is losing a lot. These are two seperate cables, I am sure he was basically saying any more complaints and we'll say your wiring is the problem!

Help please before I have to call on friday again! I am tempted to say look its still not working just come and get all your stuff and refund me!

carpy · 21-06-2007, 01:54

You can't rely on him saying the signal is "strong" on his "reader" in the loft. Strong doesn't mean anything. There's a lot more involved than the strength.

What's the actual field strength on each multiplex?
What about the C/N ratio (carrier / noise ratio)?
What's the CBER (bit error rate before correction)?
What's the VBER (bit error rate after correction)?
What's the gain of the amplifier?
What's the stated maximum output of the amplifier?
What's the actual maximum output of the amplifier?
How much are the cable runs (to TVs) attenuating the signal?

To do it properly you need to know all the above, and that's just for the Freeview. If he's saying the signal is "strong" in the loft (after the amplifier), but then weak at both the TV points, then there's something majorly wrong which he should pick up on.

Sometimes the cable which feeds the TV point might have a nail through it, or it might have been cut and plastered over by the builders etc, but not both cables......

Worst case scenario even if you have the worst possible (poorest quality) cables run to the TV points, you won't lose enough to turn a strong signal into a weak one.

Hornet · 21-06-2007, 06:41

So what could it be thats is still causing picture freeze every 20 mins or so?

Signal too strong with amp?

Aerial needs to go up 2 to 3 ft so it is above my roof line?

Picture fine on all dig channels and then freezes for a split second in most programmes watched.

He showed me the 4 digital lines on the reader and they were all above a line e said they should be above on both TVs, just lost a bit of strength by the time they reached downstairs, but nort enough to cause a problem.

As I said all signals on set top box now constant 100%.

carpy · 21-06-2007, 11:14

Quote:

Originally Posted by Hornet

So what could it be thats is still causing picture freeze every 20 mins or so?

Signal too strong with amp?

Aerial needs to go up 2 to 3 ft so it is above my roof line?

Picture fine on all dig channels and then freezes for a split second in most programmes watched.

He showed me the 4 digital lines on the reader and they were all above a line e said they should be above on both TVs, just lost a bit of strength by the time they reached downstairs, but nort enough to cause a problem.

As I said all signals on set top box now constant 100%.

Most likely the signal is overloading the amplifier but could be one of may things. It's pixellating for a reason! Sounds like the guy had some kind of cheap & nasty measuring device too. I don't hold out much hope for you!

altis · 21-06-2007, 11:50

I'd follow carpy's advice and try an attenuator between the aerial and the amp. Before you go shopping you'll need to check the connector to the amp to see if it's an 'F'-type or ordinary coax. If this solves everything then I'd let the matter rest. Though you might want to send a snotty letter to Inaction Aerials and the CAI.

If that doesn't sort it then get them back in again. You're paying top whack so you should be getting a top quality service.

Hornet · 21-06-2007, 16:35

They are coming for a third time Saturday. Different engineer to take a look. Say they have no idea why its doing it. Freezes two or three times and hour.

They did says atmospherics currently bad and my internal cable is noted as an issue. I again said two different cables and not mentioned on loft install!!!

What power attenuator should I buy and my stuff is all screw in so do I need F type?

Cheers

---------- Post added at 16:35 ---------- Previous post was at 16:24 ----------

Just found box they left I have a WFAV 425 Wolsey 4 O/P variable gain wideband masthead amplifier and power supply

Says typical gain (dB) 12 to 25
Noise figure <2.5

Turn this off I just get snow!

Additionally I have a 56 element aerial.

But I do live in a very poor reception area, I've been told when getting phone quotes from local installers.